This is incorrect. All S10 updates have supported upgrading systems
with zones. I believe what you are thinking of is that live-upgrade
does not support upgrading systems with zones. This is being
fixed in the next S10 update. It is already fixed in nevada.

Which Nevada build?

The install code changes look like they were integrated into b53. Some
of the zones support that was needed had been integrated earlier.
The bug is 6264796.

When will zone roots on ZFS be supported by live upgrade?

I don't know. Asking the install team would be your best bet.
Jerry
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